The short answer
For most of the year, UK time is 5 hours ahead of US Eastern Time. At 14:00 in London it is 09:00 in New York, Washington, Boston, Atlanta, Miami and Toronto. For a few weeks in spring and autumn the gap is 4 hours instead, because the UK and the US change their clocks on different dates.
Strictly, the comparison is rarely "BST vs EST". BST, UK summer time (UTC+1), runs from late March to late October. EST, Eastern Standard Time (UTC−5), runs from early November to mid-March. For most of the year the two sides are on BST and EDT (UTC−4), or on GMT (UTC+0) and EST. In both cases the gap is 5 hours. In fact BST and EST are never in force at the same time. The 4-hour weeks come when the UK is on GMT while the US is still, or already, on EDT.
Why the gap changes
The UK changes its clocks on the last Sundays of March and October. The US, under the Energy Policy Act of 2005, changes on the second Sunday of March and the first Sunday of November. So in spring the US moves its clocks forward two or three weeks before the UK, and in autumn it moves them back one week after.
| Dates | UK | US Eastern | Difference |
|---|---|---|---|
| Until 25 Oct 2026 | BST (UTC+1) | EDT (UTC−4) | 5 hours |
| 25 Oct to 1 Nov 2026 | GMT (UTC+0) | EDT (UTC−4) | 4 hours |
| 1 Nov 2026 to 14 Mar 2027 | GMT (UTC+0) | EST (UTC−5) | 5 hours |
| 14 Mar to 28 Mar 2027 | GMT (UTC+0) | EDT (UTC−4) | 4 hours |
| 28 Mar to 31 Oct 2027 | BST (UTC+1) | EDT (UTC−4) | 5 hours |
| 31 Oct to 7 Nov 2027 | GMT (UTC+0) | EDT (UTC−4) | 4 hours |
| From 7 Nov 2027 | GMT (UTC+0) | EST (UTC−5) | 5 hours |
The changes take effect at 01:00 UTC in the UK and at 02:00 local time in the US. Our London and New York page shows the same periods with worked examples.
A worked example
Suppose a team in London holds a weekly call with New York at 15:00 UK time.
- On Friday 23 October 2026, 15:00 in London is 10:00 in New York.
- On Monday 26 October 2026, after the UK's change, 15:00 in London is 11:00 in New York.
- On Monday 2 November 2026, after the US change, 15:00 in London is back to 10:00 in New York.
If the meeting was set up in a calendar in the London time zone, it stays at 15:00 for London and moves for New York. If it was set up in New York time, the reverse happens. Neither is wrong, but everyone needs to know which side is fixed. Calendar apps handle this correctly as long as the event has a real time zone attached. Problems come from times typed into emails and chat messages.
Other US time zones
The same pattern applies across the US, with larger gaps further west. In normal weeks:
- Central Time (Chicago, Dallas, Houston): 6 hours behind the UK.
- Mountain Time (Denver): 7 hours behind.
- Arizona (Phoenix): 8 hours behind during BST and 7 hours behind during GMT, because Arizona does not change its clocks.
- Pacific Time (Los Angeles, San Francisco, Seattle): 8 hours behind.
- Hawaii: 11 hours behind during BST and 10 during GMT.
In the mismatch weeks, each of these gaps is an hour smaller. Arizona and Hawaii are the exception: they never change their clocks, so their gap with the UK changes only when the UK changes.
Canada mostly follows the US dates, with two big exceptions from 2026. British Columbia stays on UTC−7 and Alberta on UTC−6 all year, so from November 2026 Vancouver is 7 hours behind London rather than 8, and Calgary 6 rather than 7.
Best times for UK–US calls
With a 5-hour gap, a 09:00–17:00 day in London overlaps a 09:00–17:00 day in New York from 14:00 to 17:00 UK time, which is 09:00 to 12:00 Eastern. During the 4-hour weeks the overlap grows to 13:00–17:00 UK time. Practical slots:
- 14:00–16:00 UK / 09:00–11:00 Eastern: the most reliable window, all year.
- 13:00 UK / 08:00 Eastern: acceptable for short calls if New York colleagues start early.
- West Coast: with an 8-hour gap there is no overlap between standard working days. 16:00–17:00 UK time is 08:00–09:00 in Los Angeles, so one side has to stretch. During the mismatch weeks there is one hour of genuine overlap.
The meeting planner finds these windows for any date and skips weekends.
Writing times for both sides
- Use "UK time" and "Eastern Time" (or "ET") rather than BST and EST, unless you are sure which one applies on that date.
- Remember that "EST" in a US message in July almost always means EDT. Many people say EST all year.
- For anything important, add the UTC offset: "15:00 UK time (UTC+1) / 10:00 ET (UTC−4)".
- Double-check meetings in the last week of October and the second half of March. Those are the weeks when a remembered 5-hour gap is wrong.
- For recurring meetings with people on both sides, agree which city's time is fixed and put that city's name in the invitation title, for example "Weekly sync (15:00 London)". Everyone then knows which side will see the time move.
Tools and related pages
See the live times in London and New York, convert a specific time with the converter, or read EST and EDT and BST vs GMT for more on each side's rules.
Sources
- GOV.UK, When do the clocks change?: gov.uk
- NIST, Daylight saving time: nist.gov
- IANA time zone database, release notes for 2026b and 2026c (British Columbia and Alberta): iana.org/time-zones